(Reuters) - Investa Office Fund(IOF.AX) said it has set Sept. 17 as the date for its shareholders to vote on Blackstone Group’s (BX.N) sweetened A$3.3 billion ($2.4 billion) bid.

Blackstone Group declared its A$5.52 per share offer as final. The U.S. private equity giant increased its offer for the Sydney-focused landlord last week in response to a rival bid from Canada’s Oxford Properties Group.

Oxford, which already owns 10 percent of Investa, offered A$5.50 per share compared with the U.S. buyout giant’s previous bid of A$5.3485 per share.

A Sydney-based spokeswoman for Oxford Properties Group, the real estate investment arm of Canadian pension fund OMERS, declined to comment.

Australia’s commercial property sector has defied a softening in home values. With overall unemployment sitting at a six-year low, economic growth surging and city downtown capacity barely growing, demand is outstripping supply.

The face-off between the North American firms is indicative of a reach for yield by global investors amid strong Australian commercial rents, especially in Sydney, where downtown capacity is tight.

Reporting by Chandini Monnappa in Bengaluru; Editing by Stephen Coates